The present disclosure relates to light guides and illumination devices and particularly relates to a structure of a rod-shaped light guide in which light incident on a lateral end surface thereof is guided to exit the light through an exit surface thereof which is a radially oriented surface thereof.
Some image forming apparatuses, such as multifunction peripherals, employ as a light source section for an image reading device, such as a scanner, a line light source in which a rod-shaped, resin-made light guide is combined with a light source (for example, an LED) capable of emitting light to the interior of the light guide through one lateral end of the light guide which is a longitudinal end thereof. The light source section is required to linearly illuminate an original document to be read in synchronism with reading of a line sensor. For this purpose, a surface of the light guide opposite to an exit surface thereof through which light exits the light guide is provided with light reflecting or scattering patterns, so that the patterns can deflect light, which has entered the light guide, toward the exit surface to allow linear illuminating light to exit the light guide in the direction toward the original document. For example, an image reading device is known in which a hollow light guide member is interposed between a light source and an incident surface of a light guide to reduce the increase in temperature of the light guide.